what is the difference between N-layer and N-tier architecture in LINQ?

http://www.dotnetfunda.com/interviews/show/4547/what-is-the-difference-between-n-layer-and-n-tier-architecture

1-N-layers of application may reside on the same physical computer 2-N-tier architecture usually has atleast three separate logical parts, each located on separate physical server. Each tier is responsible for a specific functionality. Each tier is completely independent from all other tiers